Amino acids which are used in various applications in the field of microorganisms and fermentation, animals and medical treatment, plants and the like are present sometimes as hydrochloride, hydrobromide, hydroiodide, sulfonate, sulfate, nitrate and the like salts, but it is known that characteristics of the amino acids vary and their flexibility varies depending on the kinds of salt.
For example, it is known that since δ-aminolevulinic acid hydrochloride (cf. Patent References 1 to 6 for its production method) contains hydrochloric acid, it causes corrosion of devices and generation of irritating odor due to hydrogen chloride vaporized during its production process and compounding and dispersing process. In addition, it is known that δ-aminolevulinic acid hydrochloride has a problem of being sensitive to high temperature heating sterilization because it has a property in that it is partially degraded at from 130 to 156° C. and completely degraded at 156° C. or more.    Patent Reference 1: JP-A-48-92328    Patent Reference 2: JP-A-62-111954    Patent Reference 3: JP-A-2-76841    Patent Reference 4: JP-A-6-172281    Patent Reference 5: JP-A-7-188133    Patent Reference 6: JP-A-9-316041